Debate has been growing in developmental psychology over how much the
cognitive development of children is like theory change in science. Useful
debate on this topic requires a clear understanding of what it would be
like for a child to have a theory. I argue that existing accounts of theories
within philosophy of science and developmental psychology either are less
precise than is ideal for the task or cannot capture everyday theorizing
of the sort that children, if they theorize, must do. I then propose an
account of theories that ties theories and explanation very closely together,
treating theories primarily as products of a drive to explain. I clarify
some of the positions people have taken regarding the "theory theory" of
development, and I conclude by proposing that psychologists interested
in the theory theory look for patterns of affect and arousal in development
that would accompany the existence of a drive to explain.